Toxicity of effluent from a titanium dioxide factory containing
sulphuric acid residue with soluble iron metallic salts and insoluble
material such as silica, etc. on fishes, decapods and molluscs was
studied. The effluent caused changes in pH and oxygen depletion of
the sea water. Sublethal effects of the precipitate of ferrous salts were
also studied. Dilutions of effluent up to 1:150 were LC100 for all
organisms used while 1:200 dilution was LC50 for fishes at 36 hr and
for other organisms at 48 hr. But death of organisms at this
concentration was caused by pH changes and oxygen depletion and did
not account for the effects of the precipitate. Below this level
precipitation started soon after mixing with sea water causing death
of organisms by choking their gills and siphons. Dilutions,< 1:1000
were 96 hr LCO.